This invention relates generally to the field of fiber optics and relates more particularly to non-linear optical waveguide components. Such a component may, for example, be a directional coupler, a mixer, a parametric amplifier or a second harmonic generator.
Dyott et al U.S. Pat. No. 4,181,515 discloses non-linear optical waveguide components which are formed by a single crystal core disposed within the cladding of an optical fiber. The crystal is formed from optically anisotropic material and is arranged such that its refractive indices along first and second transverse orthogonal axes are larger and smaller, respectively, than the refractive index of the cladding.
Dyott U.S. application Ser. No. 404,283, filed Aug. 2, 1982, entitled Self-Aligning Optical Fiber with Accessible Guiding Region and assigned to the assignee of the present invention discloses a self-aligning optical fiber comprising a core and cladding having different refractive indices and forming a single-mode guiding region. The guiding region is located sufficiently close to the surface of the fiber, along a selected length of the fiber, to allow coupling to a guided wave. The outer surface of the fiber has a non-circular cross-section with a predetermined geometric relationship to the guiding region so that the location of the guiding region can be ascertained from the geometry of the outer surface. Preferably, the guiding region of the fiber has an elliptical cross-section defining two transverse orthogonal axes which, in combination with the different refractive indices of the core and cladding, permit the de-coupling of waves polarized along such axes. The non-circular cross-section of the outer surface of the fiber preferably has a predetermined geometric relationship to the transverse axes of the elliptical guiding region so that the orientation of those axes can also be ascertained from the geometry of the outer surface.